1. Field of the Invention
The present invention relates to a magnetic device having a coil wound around a magnetic core, and more specifically to an inductance component like an inductor or a transformer, which is used in various electronics and power sources to reduce core loss using direct current bias.
2. Description of the Related Art
Recently, various electronics are becoming smaller and more lightweight. Accordingly, the relative volume ratio of a power source section to the entire electronics is tending to increase. This is because, while various circuits are subjected to large-scale integration (LSI), it is difficult to miniaturize magnetic components, such as an inductor and a transformer, which are essential for circuit elements of the power source section. Accordingly, various methods have been attempted in order to achieve miniaturization and weight reduction of the power source section.
It is effective to decrease the volume of a magnetic core composed of a magnetic material in order to obtain smaller and lightweight magnetic devices, such as an inductor and a transformer (hereinafter, referred to as an inductance component). Generally, miniaturizing the magnetic core easily causes magnetic saturation thereof. Thus, the amplitude of electric current being treated as power supply may be decreased.
In order to solve the above problems, a technique is well known to increase magnetic resistance of a magnetic core and to prevent decrease in the amplitude of the electric current therethrough by providing a part of the magnetic core with a magnetic gap. However, the magnetic inductance of the magnetic component is decreased in such a case.
As a method for preventing decrease in the magnetic inductance, a technique regarding a structure of a magnetic core using a permanent magnet for generating magnetic bias is disclosed in Japanese Unexamined Patent Application Publication No. 01-169905 (hereinafter, referred to as conventional art 1). In such a technique, a permanent magnet is used to apply direct current magnetic bias to the magnetic core, resulting in increasing the number of lines of magnetic force capable of passing through the magnetic gap.
However, since the magnetic flux produced by a coil wound around the magnetic core passes through the permanent magnet in the magnetic gap in the structure of the magnetic core of the conventional inductance component, the permanent magnet is demagnetized.
Also, the smaller the size of the permanent magnet inserted into the magnetic gap is, the larger the effects of the demagnetization due to external factors are.
Accordingly, it is an object of the present invention to provide an inductance component in which the permanent magnet being mounted has little limitation in shape, and in which the permanent magnet is not demagnetized by magnetic flux due to a coil wound around a magnetic core.
It is another object of the present invention to provide an inductance component in which generation of heat due to leakage flux of a coil wound around the magnetic core, and in which the properties of the permanent magnet and the inductor are not degraded.
According to an aspect of the present invention, there is provided a inductance component which comprises a magnetic core having at least one magnetic gap, means for generating a direct-current biased magnetic field produced by mounting at least one of permanent magnets in the vicinity of a generally closed magnetic circuit which passes through the magnetic gap in the magnetic core, and a coil wound around the magnetic core. In the inductance component, the at least one of permanent magnets are mounted in the vicinity of the magnetic gap at least one of end portions of the magnetic core. The end portions defining the magnetic gap therebetween.
According to another aspect of the present invention, there is provided an inductance component which comprises a magnetic core having at least one magnetic gap, means for generating a direct-current biased magnetic field produced by mounting at least one of permanent magnets in the vicinity of a generally closed magnetic circuit which passes through the magnetic gap in the magnetic core, and a coil wound around the magnetic core. In the inductance component, the at least one of the permanent magnets are arranged on at least one of the outside portions of the magnetic core except in the magnetic gap in the magnetic core.